Metabolomic Profile of Oviductal Extracellular Vesicles across the Estrous Cycle in Cattle

Oviductal extracellular vesicles (oEVs) have been proposed as key modulators of gamete/embryo maternal interactions. The aim of this study was to examine the metabolite content of oEVs and its regulation across the estrous cycle in cattle. Oviductal EVs were isolated from bovine oviducts ipsilateral and contralateral to ovulation at four stages of the estrous cycle (post-ovulatory stage, early and late luteal phases, and pre-ovulatory stage). The metabolomic profiling of EVs was performed by proton nuclear magnetic resonance spectroscopy (NMR). NMR identified 22 metabolites in oEVs, among which 15 were quantified. Lactate, myoinositol, and glycine were the most abundant metabolites throughout the estrous cycle. The side relative to ovulation had no effect on the oEVs' metabolite concentrations. However, levels of glucose-1-phosphate and maltose were greatly affected by the cycle stage, showing up to 100-fold higher levels at the luteal phase than at the peri-ovulatory phases. In contrast, levels of methionine were significantly higher at peri-ovulatory phases than at the late-luteal phase. Quantitative enrichment analyses of oEV-metabolites across the cycle evidenced several significantly regulated metabolic pathways related to sucrose, glucose, and lactose metabolism. This study provides the first metabolomic characterization of oEVs, increasing our understanding of the potential role of oEVs in promoting fertilization and early embryo development.